2. ACID - BASE PHYSIOLOGY DEFINITIONS ACID - can donate a hydrogen ion BASE – can accept a hydrogen ion STRONG ACID – completely or almost completely dissociates into a hydrogen ion and its conjugate base in aqueous solution WEAK ACID – only slightly dissociated in aqueous solution Strong acids usually have weak conjugate bases; weak acids usually have strong conjugate bases BUFFER – mixture of substances in aqueous solution. Usually a weak acid and its conjugate base, that can resist changes in hydrogen ion concentration when strong acids or bases are added. ACID - can donate a hydrogen ion BASE – can accept a hydrogen ion STRONG ACID – completely or almost completely dissociates into a hydrogen ion and its conjugate base in aqueous solution WEAK ACID – only slightly dissociated in aqueous solution Strong acids usually have weak conjugate bases; weak acids usually have strong conjugate bases BUFFER – mixture of substances in aqueous solution. Usually a weak acid and its conjugate base, that can resist changes in hydrogen ion concentration when strong acids or bases are added.

3. ACID - BASE PHYSIOLOGY DEFINITIONS pH - negative log of hydrogen ion concentration ACIDOSIS - pH < 7.35 ACIDOSIS - pH < 7.35 ALKALOSIS - pH > 7.45 ACIDOSIS - pH < 7.35 ACIDOSIS - pH < 7.35 ALKALOSIS - pH > 7.45

6. ISOHYDRIC PRINCIPLE – All buffer pairs in a homogeneous solution are in equilibrium with the same hydrogen ion concentration BICARBONATE PHOSPHATE BLOOD PROTEINS – especially hemoglobin INTERSTITIAL FLUID – mainly bicarbonate, some phosphate BONES – mainly phosphate in hydroxyapatite INTRACELLULAR BUFFERS – intracellular proteins and organic phosphates ISOHYDRIC PRINCIPLE – All buffer pairs in a homogeneous solution are in equilibrium with the same hydrogen ion concentration BICARBONATE PHOSPHATE BLOOD PROTEINS – especially hemoglobin INTERSTITIAL FLUID – mainly bicarbonate, some phosphate BONES – mainly phosphate in hydroxyapatite INTRACELLULAR BUFFERS – intracellular proteins and organic phosphates ACID - BASE PHYSIOLOGY BUFFERS OF THE BODY

7. CO 2 + H 2 O H 2 CO 3 H + + HCO 3 Carbonic Anhydrase Carbonic Anhydrase _ Transport of CO 2 by the Blood CO 2 (Gas phase) (Dissolved in the aqueous phase)

8. Taking Logarithms Since pH is negative logarithm

9. Henderson – Hasselbalch Equation pH = pK´ + log [HCO - 3 ] p 0.03 x Pco 2

12. [HCO 3 - ]p, mmol/ liter 15 20 25 30 35 40 pH 7.07.17.27.37.47.57.67.77.8 HCO 3 - Pco 2 HCO 3 - Pco 2 Respiratory acidosis D D A A G G E E F F C C I I H H B B Uncompensated respiratory acidosis Metabolic alkalosis and respiratory acidosis Compensated

13. Common Causes of Respiratory Acidosis  Depression of Respiratory Control Centers  Anesthetics  Sedatives  Opiates  Brain injury or disease  Severe hypercapnia, hypoxia  Neuromuscular disorders  Spinal cord injury  Phrenic nerve injury  Poliomyelitis  Botulism, tetanus  Myasthenia gravis  Administration of curare-like drugs  Diseases affecting the respiratory muscles  Pulmonary diseases  Acute asthma  Pulmonary vascular disease  Depression of Respiratory Control Centers  Anesthetics  Sedatives  Opiates  Brain injury or disease  Severe hypercapnia, hypoxia  Neuromuscular disorders  Spinal cord injury  Phrenic nerve injury  Poliomyelitis  Botulism, tetanus  Myasthenia gravis  Administration of curare-like drugs  Diseases affecting the respiratory muscles  Pulmonary diseases  Acute asthma  Pulmonary vascular disease

14. Common Causes of Respiratory Acidosis  Chest wall restriction  Kyphoscoliosis  Extreme obesity  Lung restriction  Pulmonary fibrosis  Sarcoidosis  Pneumothorax  Pulmonary parenchymal diseases  Pneumonia  Pulmonary edema  Airway obstruction  Chronic obstructive pulmonary disease  Upper airway obstruction  Chest wall restriction  Kyphoscoliosis  Extreme obesity  Lung restriction  Pulmonary fibrosis  Sarcoidosis  Pneumothorax  Pulmonary parenchymal diseases  Pneumonia  Pulmonary edema  Airway obstruction  Chronic obstructive pulmonary disease  Upper airway obstruction

15. [HCO 3 - ]p, mmol/ liter 15 20 25 30 35 40 pH 7.07.17.27.37.47.57.67.77.8 HCO 3 - Pco 2 HCO 3 - Pco 2 Respiratory alkalosis D D A A G G E E F F C C I I H H B B Uncompensated respiratory alkalosis Metabolic acidosis and respiratory alkalosis Compensated

16. Common Causes of Respiratory Alkalosis  Central Nervous System  Anxiety  Hyperventilation  Inflammation (encephalitis, meningitis)  Cerebrovascular disease  Tumors  Drugs or hormones  Salicylates  Progesterone  Pulmonary diseases  Acute asthma  Pulmonary vascular disease (pulmonary embolism)  Central Nervous System  Anxiety  Hyperventilation  Inflammation (encephalitis, meningitis)  Cerebrovascular disease  Tumors  Drugs or hormones  Salicylates  Progesterone  Pulmonary diseases  Acute asthma  Pulmonary vascular disease (pulmonary embolism)

17. Common Causes of Respiratory Alkalosis  Bacteremias, fever  Overventilation with mechanical ventilators  Hypoxia,high altitude  Bacteremias, fever  Overventilation with mechanical ventilators  Hypoxia,high altitude

18. [HCO 3 - ]p, mmol/ liter 15 20 25 30 35 40 pH 7.07.17.27.37.47.57.67.77.8 D D A A G G E E F F C C B B HCO 3 - Pco 2 HCO 3 - Pco 2 Metabolic acidosis I I H H Metabolic acidosis and respiratory alkalosis Uncompensated metabolic acidosis Uncompensated metabolic acidosis Compensated

19. Common Causes of Metabolic Acidosis  Ingested drugs or toxic substances  Methanol  Alcohol  Salicylates  Ammonium Chloride  Ethylene glycol  Loss of bicarbonate ions  Diarrhea  Pancreatic Fistulas  Renal dysfunction  Inability to excrete hydrogen ions  Renal dysfunction  Ingested drugs or toxic substances  Methanol  Alcohol  Salicylates  Ammonium Chloride  Ethylene glycol  Loss of bicarbonate ions  Diarrhea  Pancreatic Fistulas  Renal dysfunction  Inability to excrete hydrogen ions  Renal dysfunction

20. Common Causes of Metabolic Acidosis  Lactic acidosis  Hypoxemia  Anemia, carbon monoxide  Shock (hypovolemic,cardiogenic, septic, etc.)  Severe exercise  Acute respiratory distress syndrome (ARDS)  Ketoacidosis  Diabetes mellitus  Alcoholism  Starvation  Lactic acidosis  Hypoxemia  Anemia, carbon monoxide  Shock (hypovolemic,cardiogenic, septic, etc.)  Severe exercise  Acute respiratory distress syndrome (ARDS)  Ketoacidosis  Diabetes mellitus  Alcoholism  Starvation

21. [HCO 3 - ]p, mmol/ liter Metabolic alkalosis and respiratory acidosis 15 20 25 30 35 40 pH Metabolic alkalosis 7.07.17.27.37.47.57.67.77.8 D D A A G G E E F F C C I I H H B B HCO 3 - Pco 2 HCO 3 - Pco 2 Metabolic alkalosis Compensated

22. Common Causes of Metabolic Alkalosis  Loss of hydrogen ions  Vomiting  Gastric fistulas  Diuretic therapy  Treatment with or overproduction of mineralocorticoids  Ingestion or administration of excess bicarbonate  Intravenous bicarbonate  Ingestion of bicarbonate or other bases (e.g. antacids)  Loss of hydrogen ions  Vomiting  Gastric fistulas  Diuretic therapy  Treatment with or overproduction of mineralocorticoids  Ingestion or administration of excess bicarbonate  Intravenous bicarbonate  Ingestion of bicarbonate or other bases (e.g. antacids)

26. ACID - BASE PHYSIOLOGY DEFINITIONS BASE EXCESS OR DEFICIT = mEq of acid or base needed to titrate 1 liter of blood to a pH of 7.4 at 37ºC if the Pco 2 were 40 torr BASE EXCESS OR DEFICIT = mEq of acid or base needed to titrate 1 liter of blood to a pH of 7.4 at 37ºC if the Pco 2 were 40 torr ANION GAP = [Na + ] - ([Cl - ] + [HCO 3 - ]) Normally 12 ± 4 mEq / L ANION GAP = [Na + ] - ([Cl - ] + [HCO 3 - ]) Normally 12 ± 4 mEq / L If the anion gap is greater than 16 mEq / L : Lactic acidosis, ketoacidosis or organic anions Renal retention of sulfate, phosphate, or urate Decreased [K + ], [Ca ++ ], and/ or [Mg ++ ] If the anion gap is greater than 16 mEq / L : Lactic acidosis, ketoacidosis or organic anions Renal retention of sulfate, phosphate, or urate Decreased [K + ], [Ca ++ ], and/ or [Mg ++ ]

27. Acid- Base Disturbances Uncompensated respiratory acidosis Uncompensated respiratory alkalosis Uncompensated metabolic acidosis Uncompensated metabolic alkalosis Partially compensated respiratory acidosis Partially compensated respiratory alkalosis Partially compensated metabolic acidosis Partially compensated metabolic alkalosis Respiratory and metabolic acidosis Respiratory and metabolic alkalosis pH Pco 2 HCO 3 _ _

28. A Classification of the Causes of Hypoxia Increased FIo 2 helpful? Classification PAo2PAo2 P ao 2 C ao 2 C vo 2 P vo 2 Hypoxic hypoxia Low alveolar Po 2 Diffusion impairment Right to left shunts V/Q mismatch Anemic hypoxia CO poisoning Hypoperfusion hypoxia Histotoxic hypoxia Low Norm Low Norm Low Norm Low High Low High Yes No Yes No Possibly No